Variability of the past deep-water masses in the Arabian Sea over the last 41ka

Science Highlights

19 July 2026

Shukla and colleagues (2026, see reference below) propose a high-resolution (∼400-year) authigenic ƐNd record measured from a sediment core (hereafter referred to as GC10; 2,055 m water depth) located in the eastern Arabian Sea. They demonstrate that variations in the ƐNd record in this area resulted from changes in the relative proportions of southern-sourced deep-water masses, with Antarctic Bottom Water (AABW) dominating during colder periods and North Atlantic Deep Water (NADW) during warmer periods. On millennial timescales, the same balance between NADW and AABW is observed: whereas the Last Glacial Maximum and Heinrich events are characterized by greater intrusion of AABW, rapid warm climate events show a predominance of NADW. Through analysis of the Nd signature in the lithogenic material, the authors also detect a significant Ganga–Brahmaputra influence between 28 and 18 ka, likely related to an intensified northeast monsoon period.

Figure: Bathymetry map of the Indian Ocean with core locations and pathways of different water masses (brown arrows). Location of the present studied CoreSSD60‐GC10 lies in the South Eastern Arabian Sea, marked with a red star. Core SK129‐CR2 and Core SK221‐05 are shown for reference. Filled blue circles denote the seawater sampling stations. Light orange arrows shows the aeolian dust influx from the nearby continents (Bikkina et al., 2023). CDW: Circumpolar Deep Water; AABW: Antarctic Bottom Water; MNADW: Modified North Atlantic Deep Water; RSW: Red Sea Water; PGW: Persian Gulf Water;OFZ: Owen Fracture Zone; LB: Lakshadweep Basin.

Figure: Temporal variation of authigenic (HAc leachates) and detrital ƐNd values (a) and median grain size (D50) (b) of the present study compared with δ18OcarbVPDB (Oxygen isotope measured in the Carbonate and expressed relative to Vienna PeeDee Belemnite) (c) and, δ18O of NGRIP ice core (d), marked with the cold and warm climatic events/periods. Numbers indicate the Dansgaard‐Oeschger interstadials. The red color line shows the 5‐point moving average of δ18O of the NGRIP core. Radiocarbon (14C) dates of the GC10 core are marked on the X‐axis with gray diamonds.

Reference:

Shukla, A., Mishra, T. K., & Singh, S. K. (2026). Tracking the Millennial Scale Variability of Deep Water Circulation and Lithogenic Influence in the Arabian Sea Over the Past 41 ka Through Nd Isotope. Paleoceanography and Paleoclimatology, 41. Access the paper:10.1029/2025pa005310

Latest highlights

Continuous record of the Antarctic Circumpolar Current latitude over the last glacial-interglacial cycles

The meridional positions of the oceanic fronts separating subtropical and Antarctic waters are key to constraining the mechanisms that drive the degassing of deeply-stored CO2 at the end of the glacial periods…

23 Million Years of iron sources reconstructed in the Northwest Pacific Ocean using iron isotopes in a ferromanganese crust

Using iron isotopes and elemental records, Chu and co-workers analysed an iron-manganese crust recovered from the Hongyan Seamount, and reconstructed the sources of dissolved Fe to the Northwest Pacific Ocean…

Arctic outflows to Davis Strait and the Labrador Sea traced by radionuclide distributions

This study demonstrates that Arctic outflows through the Canadian Arctic Archipelago play a much more significant role than previously recognised.

Zinc and lead isotopes reveal human footprint on the most remote oceanic regions

Benaltabet and co-workers analysed suspended particles collected on GEOTRACES GP21 cruise tracked from Chile to New Caledonia.

Rechercher